Synthetic fibers, e.g., polyester (PES), polyamide, acrylic and acetate fibers, can be exhaust-dyed with disperse dyestuffs by the high-temperature method at a temperature of about 105.degree. C. to about 140.degree. C., preferably about 130.degree. C., or by the boiling temperature method at a temperature of about 95.degree. C. to about 100.degree. C. in the presence of carriers.
However, only a few selected disperse dyestuffs can produce all depths of shade when dyeing at the boil, which is carried out in open-type dyeing machines under atmospheric pressure. Despite the use of a carrier, many disperse dyestuffs only produce pale to medium depths of shade by this method.
In the field of coloring yellow hues on PES fibers under boiling temperature conditions, C.I. Disperse Yellow 54 and 64 have become established in industry as the most important yellow dyestuffs derived from quinophthalones for the self-shade and combination-shade dyeing. Disperse Yellow 54 and 64 produce bright reddish yellow dyeings having a high lightfastness level; though these dyestuffs are, in principle, suitable for all depths of shade both in dyeing at the boil and in high-temperature dyeing, they have, nevertheless, a number of disadvantages. Thus, the tinctorial strength is, as is typical for quinophthalone dyestuffs, relatively low. As a consequence thereof, dyestuff consumption and hence costs, are high, particularly in the case of deeper shades. Further, the dyeing of wound packages (cheese, muff or beam dyeing), in hank and piece dyeing, and in modern self-shade and combination-shade rapid dyeing methods, there is always a great danger of the finished dyeing being unlevel. Disperse Yellow 54 and 64 are particularly poor-leveling dyestuffs, unless an excessively long dyeing time is used for leveling out the dyeing. Finally, when the concentration of the dyestuff used relative to the weight of the PES fiber material is increased, the hue becomes undesirably more and more reddish, and consequently deep, neutral yellow dyeings are no longer obtainable.
As far as the field of yellow colorations of PES fibers under high-temperature dyeing conditions is concerned, azo dyestuffs of the hydroxypyridone type (e.g. C.I. Disperse Yellow 114, 180, 227 and 230) have become established in industry as important yellow dyestuffs for the self-shade and combination-shade dyeing. These dyestuffs produce bright greenish yellow dyeings having a high lightfastness level. They are suitable for dyeing all depths of shade under high-temperature dyeing conditions and are characterized by high tinctorial strength and consequently by low dyestuff consumption and low costs. However, these dyestuffs also have disadvantages. The distribution equilibrium at the end of the dyeing process (i.e., amount of dyestuff in the fiber compared with amount of dyestuff in the dyeing liquor) is such that, depending on the depth of shade being dyed, a certain amount of dyestuff does not exhaust onto the PES fiber. Moreover, a number of these dyestuffs are phototropic, so that it can be very difficult, depending on the optical conditions, to compare a sample of a completed dyeing with that of the shade to be matched. Further, a number of these dyestuffs are pH-sensitive, i.e., at a dyeing pH above 5 a considerable amount of the dyeing strength is lost, and no dyestuff of the hydroxypyridone type is suitable for dyeing at the boil, even in the presence of carriers. This means that the color build-up achieved under these dyeing conditions is low or at most of medium depth, which results in a high portion of non-exhausting dyestuff residue remaining in the dyebath. Consequently, dyestuffs costs are extremely high because of low dyestuff utilization, and it is impossible to obtain deep self-shade or combination-shade dyeings with this type of dyestuff.
The object of the present invention is to avoid the above-described disadvantages of the disperse-type yellow dyestuffs already known for use in the exhaust dyeing of synthetic fibers, such as polyamide, PES, acrylic and acetate fibers, in particular PES fibers, and their mixtures with other fibers.